The present invention is based on a method and apparatus for voltage regulation depending on the charge state of a battery, especially for regulation of a voltage produced by a generator, which charges the battery and supplies consuming devices.
Methods and devices for controlling the voltage produced by a generator, which is required for charging a battery and supplying consuming devices, are known.
The charge of a battery in a motor vehicle can decrease to an undesirably low value, because of critical vehicle conditions, particularly when the vehicle has a low speed and simultaneously the connected consuming devices are consuming a high power. For reliable voltage regulation it is necessary to detect and consider the power supply load and the actual charge of the battery. It is also necessary to determine the charge on the battery in different time intervals as is set forth, for example, in German Published Patent Application 32 43 075. The battery can be separated from the power supply for a short time by an electronic controller and connected with a test resistor. The voltage, which exists between the battery terminals, can be used as a measure of the charge of the battery considering the battery temperature. If it is determined that the charge state of the battery is under a certain permitted value, suitable measures can be taken, for example, the rotational speed of the engine can be increased or the consuming device load can be reduced so that the charge state can improved during the following vehicle time.
It is disadvantageous that the battery be separated from the power supply net during the regulation of the voltage from the generator. Furthermore, if it is so disconnected, no information can be obtained on the size of the power supply network load.